Results 1 to 10 of 10

Thread: Evohome - boiler 6min on, 4min off and so on?

  1. #1
    Automated Home Jr Member
    Join Date
    Oct 2016
    Location
    Scotland
    Posts
    11

    Default Evohome - boiler 6min on, 4min off and so on?

    Hello,

    I have installed evohome 2 days ago. Its seems to worked well yesterday however last night I noticed something strange.
    I have HR92 in 3 bedrooms, living room one radiator with HR92 and one radiator without, bathoorm radiator without hr92. BDR91 on combi boiler

    HR92 - set to -1 to compensate, 6 cycles on Evo.

    I set the temp at night as follows: living 17C, bedroom 20,20, 21

    I woke up last at night and noticed that boiler started to work for 6min then 4min off, 6min on - 4min off and so on.
    Checked all radiators and they were barely warm with bathroom on hot (no hr92 on it). Temp in all badrooms were 1C above set temp on evohome.

    I put the temp down to 17 in all bedrooms and the strange behavior stopped.

    Could someone advise what has caused the boiler to come on for 6min and then off for 4min?

    Thanks

  2. #2
    Automated Home Legend paulockenden's Avatar
    Join Date
    Apr 2015
    Location
    South Coast
    Posts
    1,620

    Default

    Are your radiators properly balanced?

    It might be that one of the HR92s was wide open, and required that duty cycle to keep the room at the required temp, because most of the flow was going through the bathroom rad.

    Try the same thing tonight, but set the bedrooms down to 17 individually, until you can identify which one is creating this demand. Then see if the lockshield is almost closed on that radiator.

  3. #3
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    1,885

    Default

    Probably not directly related to your problem, but having two radiators in your living room but an HR92 on only one of them is going to cause you problems IMHO.

    For a given zone (room) you should either have all HR92's or none. Does the radiator without the HR92 have a standard TRV or nothing at all ?

    The temperature sensor in the HR92 is going to pick up the room heating up from the radiator that it can't control - a radiator that will get hot any time the boiler is running, subject only to a manual TRV valve if it has one. This will cause the HR92 to try to close down in an attempt to get the room temperature down. So depending on where you set that manual TRV you're going to find either one radiator is hot and the other is cold or vica versa.

    As for your main problem - I would agree with Paul that it could be a balancing issue where your bathroom rad is not balanced at all (the lockshield valves are completely open) thus it steals most of the flow away from the HR92's when they have their valves in a partially open state.

    The Evohome will keep increasing the duty cycle of the boiler until it can satisfy the rooms it controls with HR92's - it is unaware that your bathroom radiator is stealing a lot of the heat.

    The problem with trying to balance the bathroom radiator is it might be a bypass radiator if you have no automatic bypass valve, so restricting it too much might cause boiler lockouts. Do you know if your system has an automatic bypass valve fitted ?

    Another possibility is that the HR92's have not had time to calibrate themselves properly - it can take them a little while (hours to days depending on use) to figure out where the "opening point" of your TRV valve bodies is, until that happens they might call for heat when there is actually no flow through the radiator, because the valve is only just closed but the HR92 thinks it is slightly open.

    This could also be a result of incorrectly installing the HR92 by not unscrewing the hand wheel before fitting it, preventing it self calibrating. So I'd recommend doing the following:

    For each HR92, unclick the latch and lift it off the threaded base. Turn the black wheel fully anti-clockwise - if the heating is running you should hear the radiator flow and it will start to get hot. Put the HR92 back on and click the latch closed. Set the temperature to a high setting like 30 by turning the knob on the top and wait a few minutes.

    After about a minute it will start closing the valve to calibrate the closed position and it will say "CYCLE" on the screen. You will hear it wind down the valve slowing down as it does and then stop for a moment. After this it will fully open the valve, (because you set it to 30) wait until it finishes doing this, now the fully open position will be calibrated. Now set the temperature back to normal.

    This should get the calibration of the valve a lot closer, after that you just need to let it operate normally for a few days and it will eventually calibrate the opening point of the valve precisely so it knows exactly at what point your TRV valve bodies start flowing.

    Sticky valve bodies could also cause what you see, but see if calibration helps first.
    Last edited by DBMandrake; 30th October 2016 at 11:19 AM.

  4. #4
    Automated Home Guru
    Join Date
    Oct 2016
    Location
    Bath, UK
    Posts
    151

    Default

    It would be useful to know what firmware your system is there are 2 wifi and application. Press and hold Device Settings for >10-secs the version then come up.

  5. #5
    Automated Home Jr Member
    Join Date
    Oct 2016
    Location
    Scotland
    Posts
    11

    Default

    Thanks I will give it a go properly tomorrow,

  6. #6
    Automated Home Jr Member
    Join Date
    Oct 2016
    Location
    Scotland
    Posts
    11

    Default

    Quote Originally Posted by DBMandrake View Post
    Probably not directly related to your problem, but having two radiators in your living room but an HR92 on only one of them is going to cause you problems IMHO.

    For a given zone (room) you should either have all HR92's or none. Does the radiator without the HR92 have a standard TRV or nothing at all ?

    The temperature sensor in the HR92 is going to pick up the room heating up from the radiator that it can't control - a radiator that will get hot any time the boiler is running, subject only to a manual TRV valve if it has one. This will cause the HR92 to try to close down in an attempt to get the room temperature down. So depending on where you set that manual TRV you're going to find either one radiator is hot and the other is cold or vica versa.
    2 radiators are good 10 meters away from eachother, second rad has standard TRV fitted. I may close the TRV on temporarly to stop confusing evo.



    Quote Originally Posted by DBMandrake View Post
    As for your main problem - I would agree with Paul that it could be a balancing issue where your bathroom rad is not balanced at all (the lockshield valves are completely open) thus it steals most of the flow away from the HR92's when they have their valves in a partially open state.

    The Evohome will keep increasing the duty cycle of the boiler until it can satisfy the rooms it controls with HR92's - it is unaware that your bathroom radiator is stealing a lot of the heat.
    I think you may be right here, bathroom rad is the closets one to the boiler. I will try to figoure out how to close valves. never done it before.


    Quote Originally Posted by DBMandrake View Post
    The problem with trying to balance the bathroom radiator is it might be a bypass radiator if you have no automatic bypass valve, so restricting it too much might cause boiler lockouts. Do you know if your system has an automatic bypass valve fitted ?
    Not sure what automatic bypass valve is but probably i dont have it.

    Quote Originally Posted by DBMandrake View Post
    Another possibility is that the HR92's have not had time to calibrate themselves properly - it can take them a little while (hours to days depending on use) to figure out where the "opening point" of your TRV valve bodies is, until that happens they might call for heat when there is actually no flow through the radiator, because the valve is only just closed but the HR92 thinks it is slightly open.

    This could also be a result of incorrectly installing the HR92 by not unscrewing the hand wheel before fitting it, preventing it self calibrating. So I'd recommend doing the following:

    For each HR92, unclick the latch and lift it off the threaded base. Turn the black wheel fully anti-clockwise - if the heating is running you should hear the radiator flow and it will start to get hot. Put the HR92 back on and click the latch closed. Set the temperature to a high setting like 30 by turning the knob on the top and wait a few minutes.

    After about a minute it will start closing the valve to calibrate the closed position and it will say "CYCLE" on the screen. You will hear it wind down the valve slowing down as it does and then stop for a moment. After this it will fully open the valve, (because you set it to 30) wait until it finishes doing this, now the fully open position will be calibrated. Now set the temperature back to normal.

    This should get the calibration of the valve a lot closer, after that you just need to let it operate normally for a few days and it will eventually calibrate the opening point of the valve precisely so it knows exactly at what point your TRV valve bodies start flowing.

    Sticky valve bodies could also cause what you see, but see if calibration helps first.
    Right again, I think the issue might have been caused by incorrectly installing TRVs, I figure out the above this morning and turned the black wheel fully anti-clockwise - however I have not done the rest. I will try the rest tomorrow.
    I still cannot figure out if I need to use Full Stroke on Standard.

    thank you for your time replying

  7. #7
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    1,885

    Default

    Normally you would use Standard. Full Stroke is only if you have a valve that is stiffer than normal or needs more pin travel than typical.

    You might need to enable Full Stroke if the valve didn't close fully or didn't open fully, but doing so will reduce battery life a lot and might lead to temperature overshoots as well, as it causes the HR92 to turn the valve further for the same error in room temperature.

  8. #8
    Automated Home Jr Member
    Join Date
    Oct 2016
    Location
    Scotland
    Posts
    11

    Default

    Quote Originally Posted by DBMandrake View Post
    Normally you would use Standard. Full Stroke is only if you have a valve that is stiffer than normal or needs more pin travel than typical.

    You might need to enable Full Stroke if the valve didn't close fully or didn't open fully, but doing so will reduce battery life a lot and might lead to temperature overshoots as well, as it causes the HR92 to turn the valve further for the same error in room temperature.
    I have fully cycled all HR92 and adjusted lockshield valve on towel radiator so its barley open now, hopefully it will not steal the heat from other radiators.

    One thing I noticed is that on 2 radiators hot water flows via TRV not the lockshield - from what I've read this is not how it supposed to be. Not sure why it has been setup this way. Maybe plumber had a bad day.

    I think it going to be cold tonight so I hopefully evo will work ok.
    Last edited by m112; 31st October 2016 at 05:02 PM.

  9. #9
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    1,885

    Default

    Older TRV valve bodies could only be installed with the correct flow direction, and that generally meant they had to be on the return side for the flow to be in the right direction, indicated with an arrow. Measuring the temperature at the return side is supposedly a little more accurate because that side of the radiator isn't as hot but I'm not sure that it makes a big difference.

    Modern TRV valve bodies are bidirectional and can be installed either way (although I think there is still a slight preference to installing it on the return side) and this is indicated by double arrows pointing in both directions.

    Do you see a single arrow or double arrows on the TRV valve bodies themselves ?

    Some of my TRV's are on the return side and some are on the flow side - that's just the way that they were installed (not by me) and in a couple of places there wasn't really any choice due to other obstructions, but they are all bi-directional valves so it's not a concern.

    The main problem you would get installing a uni-directional valve backwards is "water hammer" which will cause the valve or pipes to hammer/shudder at a critical opening. This will make a lot of noise and eventually damage the valve.
    Last edited by DBMandrake; 31st October 2016 at 05:12 PM.

  10. #10
    Automated Home Jr Member
    Join Date
    Oct 2016
    Location
    Scotland
    Posts
    11

    Default

    Hello,

    All seems to be working well.

    Thank you for your all your help.

    M

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •